(1) Field of the Invention
The present invention relates to a method and an apparatus for joining two substrates with an adhesive sheet interposed therebetween.
(2) Description of the Related Art
In a conventional semiconductor wafer (hereinafter, simply referred to as “wafer”), a number of elements are formed on the wafer, the back side of the wafer is ground in a back grinding process. After that, the resultant wafer is cut into each element in a dicing process. It is recent trend, however, to thin the wafer to as small as 100 μm to 50 μm, or even about 25 μm for conforming to the requirement of high density packaging.
Such a wafer that is made thinner in the back grinding process is not only brittle but also has distortion; therefore, its handlability becomes considerably poor.
In view of this, there has been suggested and practiced an approach to enhance a wafer by joining the wafer and a glass plate or the like with an adhesive sheet interposed therebetween.
To be more specific, a wafer having an adhesive tape previously adhered to the upper face is mounted and fixed on a holding stage. At a position above this wafer, a base formed of a glass plate or the like (substrate in the present invention) is latched and held at an upper end of a base supporting part in an inclined position. Then, a press roller moves on the surface of the base supported in inclined position and, also, the base supporting part moves downward according to the movement of the press roller, so that the base is joined to the semiconductor wafer (see JP-A 2000-349136.)
In the above-described conventional substrate joining apparatus, since the base for reinforcement is latched and held at the upper end of the cylindrical base supporting part surrounding the wafer, the reinforcing base has inevitably a larger diameter than the wafer. For this reason, the outer circumference of the base partly protrudes from the outer circumference of the wafer that has been reinforced by joining the base. This protrusion of base hinders the subsequent process of the wafer and makes the apparatus bulky.